1. Field of the Invention
This invention relates to a change-speed apparatus for a tractor, as is constructed for transmitting engine power to running travel apparatuses via a main change-speed mechanism, an auxiliary change-speed mechanism and a forward-and-rearward-travel-shifter mechanism.
2. Description of the Prior Art
It has originally been the general practice to construct the said forward-and-rearward-travel-shifter mechanism as is included in the main change-speed mechanism, as a portion thereof, and to cause same to be maneuvered with a single maneuvering lever provided on the main change-speed mechanism. With such forward-and-rearward-travel-shifter mechanism, being thusly incorporated in the main change-speed mechanism, it has generally been structurally restricted to provide the rearward travel in only one single step. Such restriction causing inconvenience in the change-speed apparatus of a vehicle frequently used in the rearward travel as well, such as a tractor; it has by and by become the practice to provide the forward-and-rearward-travel-shifter mechanism independently of the main change-speed mechanism, as mentioned hereinbefore.
Such independent structure enables the so-called shuttle maneuvering, i.e. maneuvering the forward and rearward running travel shifting while selectively maintaining the multi-step main speed changing in any desired change-speed position, independently of such shifting, thus to make the tractor very convenient in performing the work frequently using the rearward running travel as well. Such structure, provided with the respective maneuvering levers for enabling to independently maneuver the main change-speed mechanism and the forward-and-rearward-travel-shifter mechanism, requires accordingly as a matter of course to frequently repeat maneuvering the said two levers in order to realize a change-speed position as desired in the forward running travel and another change-speed position as may be desired in the rearward running travel.
It has therefore been desired to facilitate the maneuvering of the said two maneuvering levers in such change-speed apparatus capable of realizing the shuttle maneuvering, and to simplify the structure for such maneuvering.